A re-evaluation of the armoured catfish species of Hypostomus in the Rio Jaguaribe, north-eastern Brazil, was prompted by the discovery of specimens with pale spots on a dark background collected from that basin c. 1936 and deposited at the Academy of Natural Sciences of Philadelphia. Recent field collections in the Rio Jarguaribe basin confirmed the presence of the pale-spotted specimens and its distinctiveness as a new species. Hypostomus sertanejo n. sp. is diagnosed from other species of Hypostomus by having fins and dermal-plated regions of head and body with pale spots or vermiculations on darker background, teeth slender, asymmetrically bicuspid and numerous (34–75) on dentary and premaxilla, depressed dorsal-fin spine not reaching adipose spine, unbranched pectoral-fin spine longer than unbranched pelvic-fin ray, seven branched dorsal-fin rays and one (rarely two) predorsal plate(s) bordering supraoccipital. Ancistrus salgadae Fowler 1941 is hypothesized to be a junior synonym of Hypostomus carvalhoi (Miranda-Ribeiro, 1937), a dark-spotted Hypostomus described from the Rio Granjeiro, a tributary to the upper Rio Salgado.

Etymology: The specific epithet, sertanejo, is derived from the Portuguese word for a person from the sertão. Sertão refers to the inland xerophitic region of north-eastern Brazil that is isolated from urban centres and associated with the Caatinga and the Cerrado biomes. Sertanejos are known to be shy and elusive as well as rustic and resilient. A noun in apposition.